1. Field of the Invention
The invention concerns a turbine blade and, more particularly, can concern a hollow blade of a gas turbine rotor, of the high-pressure type, of a turbojet engine.
2. Description of the Related Art
As illustrated in FIGS. 1 and 2, it is known to provide, at the distal tip 3 of a hollow blade 2, an open cavity 5, or “bathtub”, defined by a bottom wall 7 that extends over the entire tip of the blade and by a side wall made up of two rims 9 and 10. These rims extend between the leading edge 12 and the trailing edge 14 of the blade. The rim 9 extends the wall 8 on the lower surface of the blade and the other rim 10 extends the wall 11 on the upper surface of the blade. These rims are hereinafter called upper surface and lower surface rims.
The rims 9 and 10 make it possible to ensure a wear zone between the bottom wall 7 and the casing 16 that makes it possible to absorb the contact between the distal tip of the blade 3 and the casing 16. Moreover, they make it possible to limit the passage of gas from the upper surface toward the lower surface generating aerodynamic losses that are detrimental to the yield. Due to the high temperatures of the gases passing through the turbine and the high rotational speeds of the blade, the walls of the blade and of the cavity 5 can locally reach critical temperatures.
Document EP 1 221 537 proposes cooling these walls by forming an opening on the side wall of the cavity in the vicinity of the leading edge of the blade, preferably on the lower surface side. Moreover, this opening may potentially have a small inner rim that channels the gases entering the cavity through said opening. However, the solution proposed by this document does not allow sufficient cooling of several zones of the cavity.
Indeed, the gradient of the temperatures T of the gases in the vicinity of the blade depending on the height H of the vein of the gases (FIG. 3) is particularly damaging for several zones of the cavity. Thus, this gradient of the temperatures combined with the topology of the gas flows along the blade makes the hottest gases impact the critical zone C of the blade. This zone C is situated at the tip 3 of the blade in the vicinity of the trailing edge 14, on the lower surface side 8.